Hey there! I personally haven't used external DNS tools, but my perspective is this: if your DNS is hosted in cPanel, everything is automated. Make a sub/addon domain? DNS is created automatically. Create a new account? All DNS is just instantly done.
If you have third-party DNS, you need to copy all those records over to your provider and manage things in two places.
If you have third-party DNS, you need to copy all those records over to your provider and manage things in two places.